Hackers stealing your account

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I recently heard on the news of people hacking into computer systems and stealing people's itune accounts, depleting their money by buying all these things off of itunes. The real account holder will get the bill and when they go to check or change their account, they can't because the hacker has changed all the passwords and whatnot. Then about a week after I heard about this, when I logged onto my account, it claimed that I was logging on using a different computer which is ridiculous since I'm using the same computer I always do. So I deleted all my credit card information and haven't signed on since. Has anything similar happen to you or anyone you know? What should I do next?